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I agree. This feature is also useful for admin scripts which needs to distinguish between "external" and LDAP users.

I attached a patch for this feature. auth_source_id only gets visible for admin users in it, as I do not see the need for standard users.
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@Toshi MARUYAMA : Do you have an opinion on this issue?
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What is the status of this issue?
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I think the response should include not only id but also name. Maybe the response does not include "auth_source" if the user uses internal authentication.

<pre><code class="json">
{
"user": {
"id": 1,
"login": "admin",
"firstname": "Redmine",
"lastname": "Admin",
"created_on": "2006-07-19T17:12:21Z",
"last_login_on": "2019-09-06T06:37:53Z",
"auth_source": {
"id": 1,
"name": "LDAP test server"
}
}
}
</code></pre>
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Here is a patch to add auth_source to the response of @GET /users/:id.(xml|json)@. auth_source is included only when the users auth_source is not nil and the current user is an administrator.

<pre>
"auth_source": {
"id": 1,
"name": "LDAP test server"
},
</pre>
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relates,New,23306,Support for authentication sources in REST API
relates,New,36659,Add "auth_source_id" to GET request for Endpoint /users.:format